Add AsyncListenSocket, as alias for AsyncPacketSocket

A preparation for splitting server sockets out into a separate
interface, see https://webrtc-review.googlesource.com/c/src/+/232607.

Transition plan:

1. Land this cl.

2. Update downstream code to use the new name.

3. Attempt landing
   https://webrtc-review.googlesource.com/c/src/+/232607. May need
   additional steps to not break downstream implementations of
   PacketSocketFactory::CreateServerTcpSocket.

Bug: webrtc:13065
Change-Id: Ife448c705222f4c9f66a096e3dc7eb07e0f9c3af
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/233700
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#35155}
diff --git a/api/packet_socket_factory.h b/api/packet_socket_factory.h
index 79f48f2..a46ba27 100644
--- a/api/packet_socket_factory.h
+++ b/api/packet_socket_factory.h
@@ -59,7 +59,7 @@
   virtual AsyncPacketSocket* CreateUdpSocket(const SocketAddress& address,
                                              uint16_t min_port,
                                              uint16_t max_port) = 0;
-  virtual AsyncPacketSocket* CreateServerTcpSocket(
+  virtual AsyncListenSocket* CreateServerTcpSocket(
       const SocketAddress& local_address,
       uint16_t min_port,
       uint16_t max_port,